MECHANICAL AND USEFUL ARTS. 15 



CONSTRUCTION OP ARTILLERY. 



This important subject will be found noticed in other portions of 

 -the present section of the Year-Booh, by several inventors. Early 

 in the Session of the Institution of Civil Engineers, a paper was 

 read "On the Construction of Artillery, and other Vessels, to resist 

 great internal pressure," by Mr. T. A. Longridge, C.E. ; the in- 

 quiry being limited to the question, how to make a gun of sufficient 

 strength to enable the artillerist to obtain the full effect of the ex- 

 plosive compound used in it. 



The attention of the author was drawn to the subject early in the vear 1855 

 following up the reasoning of Professor Barlow, on hydraulic-press 'cylinders' 

 he was led to consider how the internal defect of any homogeneous cylinder 

 could be remedied. Professor Barlow had shown, that in every such cylinder 

 the increase of strength was not in proportion to the increase of thickness and 

 that a vessel ot infinite thickness could not, ultimately, resist an internal pressure 

 greater than the tensile forces of the material of which it was composed The 

 material at the internal _ circumference might, in fact.be strained to its utmost 

 when that at the outside was scarcely strained at all. To remedy this it was 

 necessary that each concentric layer of the gun, or cylinder, shoidd be in an initial 

 state 'Of stress, such that when the pressure was applied, the sum of the initial 

 and the induced stresses should be a constant quantity, throughout the whole 

 thickness or the cylinder. It occurred to the author that this could be accom- 

 phshed by forming the gun, or cylinder, of a thin internal shell, or case and 

 coiling round it successive series of wires, each coil being laid on with the tension 

 due to its position. 81UU 



The principle of building up a gun in successive layers, with increasing initial 

 tension, was therefore, that which it was intended to bring forward in this paper 

 The author claimed no exclusive merit for this idea. Although then unknown to 

 him, it was being followed up by Captain Blakeley, Mr. Mallet, and others who 

 however, sought for its practical outcome in rings, or hoops, contracted or 

 forced on to the central core. Captain Blakeley had, equally with the author 

 the idea ot making use oi wire, although his experiments were entirely confined 

 to hoops It was in complete ignorance of what others were doing, that the 

 author undertook the experiments recorded, and described in detail in the present 

 paper. 1 ne results were so striking that he lost no time in bringing them before 

 the A\ ar Department. 1 he usual reference was made to the Select Committee at 

 \\ oolwich, with the usual result. The principle was pronounced to be defective 

 and not such as to warrant any trials at the public expense. The author how 

 ever, continued his experiments, and the results were such as entirely to confirm 

 his confidence in the practical utility of the invention 3 comlrm 



It was stated that these cylinders could be made at one-fourth the weight and 

 at about one-half the cost, of the ordinary hydraulic-press cylinders; and'that 

 their lightness was of great importance, when intended for export to South 

 fld not exist countries > where th ? means of transport for heavy machinery 



The discussion upon this paper extended over five evening • and 

 an abstract of the whole, with an account of Mr. Longrid°-e°s expe- 

 riments, has been reprinted, by permission of the Institution, from 

 their Proceedings ; extending in the whole to 172 octavo pa^es 

 lUustrated with diagrams. The pamphlet, with the advantage of 

 the editorship of Mr. Charles Manby, F.R.S., Hon. Sec, and Mr 

 J. iorrest, Sec, is a most valuable contribution to the science of the 

 subject, wLich now commands so large a share of public attention 

 at home and abroad. ' 



